Percussive tool such as hammers and pile drivers



X G c w W M D Filed May 9, 193

DUNCAN MARLOR WILCOX,

Mama 5,

Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE PERCUSSIVE TOOL SUCH As HAMIMERS AND PILE DRIVERS Application May 9, 1934, Serial No. 724,747 In Great Britain March 28, 1933 4 Claims. (Cl. 123-7) This invention relates to improvements in percussive tools such as hammers and pile drivers of the type in which the explosion or combustion of gases in a cylinder causes the latter to move relatively to a piston and the return movement of the cylinder delivers the blow on to an anvil.

According to the present invention the supporting rod affixed to the anvil engages with the power piston in a non-rigid manner to allow of relative displacement between them, the distance between them when at the maximum distance apart forming a space into which air is admitted, such air being used for scavenging the working cylinder of the products of combustion and for forcing into the cylinder a fresh mixture charge.

In order that the nature of the invention may be clearly understood a construction of the improved percussive tool will be described with reference to the accompanying drawing, in which Fig. 1 is a central vertical section, with certain parts in elevation, of the tool in the position occupied immediately after delivering its blow;

Fig. 2 is a similar view of the tool in the position occupied when fully extended.

Referring to the drawing the tool is constructed with two cylinders I and 2 arranged one above the other and so connected that they will move upwards and downwards together with practically no relative movement, a stop 3 being arranged at the bottom of the upper cylinder I. The power piston 4 is arranged in the upper cylinder I and is carried on the upper end of a rod 5 which passes down through the stop 3 and the lower end of the cylinder I andcarries at its lower end a second piston 6 which, when the two cylinders I and 2 are in the lowest position illustrated in Fig. 1 is at the top of the cylinder 2. On cylinder 2 is a hammer 2a..

A supporting rod I is aflixed at its lower end 8 to the anvil 9 of the tool and to its upper end III is rigidly connected a third piston II, this third piston I I being at the top of the lower cylinder 2 in contact with the second piston 6 when the two cylinders I and 2 are in their lowest position.

An exhaust port or a. ring of ports I2 is formed in the wall of the upper cylinder I in such a position that the port or ports is or are uncovered by the power piston 4 when the latter is supported by the stop 3 at the bottom of the upper cylinder I.

An outlet I3 is also formed in the wall of the lower or pumping cylinder 2 in such a position that it will be immediately below or on a level with the lower side of the second piston 6 when the cylinders are in the position in which the power piston 4 is supported by the stop 3. This outlet port I3 communicates by a suitable pipe I4 and automatic inlet valve I5 with the space I6 at the top of the upper cylinder I above the 5 power piston 4 through a suitable carburetting device I'l arranged in this pipe, the carburetor being shown diagrammatically as consisting of a part I'Ia, through which the fuel is conveyed to the bore of the choke I'Ib. 1a

A one-way inlet valve I8 for air is arranged in the wall of the pumping cylinder 2 preferably on the same level as the outlet port I3.

The upper end of the power cylinder I is closed by a cylinder head I9 which carries a sparkin i5 plug and the inlet valve I5.

In operation and whilst delivering each blow the lower end of the pumping cylinder 2 rests on the anvil 9 as shown in Fig. 1, while the piston 6 on the lower end of the rod 5 and the piston 20 II on the upper end of the supporting rod 1 are in contact and the clearance space I6 between the power piston 4 and the cylinder head I9 is filled with a compressed mixture of air and fuel. The anvil 9 rests upon or is rigidly con- 2 nected to the upper end of a pile or other object driven. Ignition of this mixture is eifected by a spark at the points of the sparking plug 20 (through wires, by an ignition coil and a battery and a suitable circuit breaker, or through wires and a magneto, not shown). The pressure caused by the ignition of the mixture throws the two cylinders I and 2 upwards into the position shown in Fig. 2. The products of combustion are exhausted through the port or ring of ports I2 when the latter have risen above the piston 4. The power piston 4 and the second piston 6 on the same rod 5 are moved upwards by the stop 3 engaging the underside of the said power piston 4, so that the second piston 6 is displaced relatively to the third piston II on the upper end of the supporting rod 1 as shown in Fig. 2, whereby air is drawn into the intervening space ZI through the one-way air inlet valve I8. At the end of the stroke the air valve I8 closes and as the cylinders I and 2 descend the air which is compressed between the two pistons 6 and II is forced through the outlet port I3 and along the pipe I4 through the carburetting device II where suflicient fuel is added to form an explosive mixture, and then past the inlet valve I5 into the space I6 at the top of the power cylinder I,

This incoming charge scavenges most of the remaining products of combustion from the power cylinder I through the exhaust port or ports I2 and leaves a fresh mixture charge to be compressed by the power piston 4 as the downward motion 01' piston 4 is arrested when pistons 6 and II come into contact. The lower end of the bottom cylinder 2 then falls on to the anvil 9 and delivers a blow thereto, the effect of such blow being preferably increased by suitably weighting the lower cylinder 2.

A conventional high-tension magneto 25 is supported upon the hammer 2a by means oi a platform or bracket 26. In the rising and falling of the hammer the weight 23 describes an arc and upon the impact of the hammer with the anvil 9 the Weight 23 causes the arm 22 to swing. This arm is connected to the spindle of the magneto 25 and when rotated, due to the sudden stopping of the hammer, a current is produced which is transmitted to the spark plug for sparking purposes to ignite the fuel in the power cylinder. The weight and arm 22 are held in elevated position by means of a spring 24 which yieldingly permits the weight to descend on the sudden stopping of the hammer.

The tool has now completed one cycle of the operation and this cycle is again repeated indefinitely.

What I claim and desire to secure by Letters Patent is:-

1. Improved percussive tool such as a hammer or pile driver of the kind referred to, comprising an anvil, a rod secured at its lower end to the anvil and having at its upper end a pumping piston, said rod supporting at its upper end in a non-rigid manner to allow of relative displacement a second pumping piston having secured thereto a power piston, means to supply air to the space between the two pumping pistons when separated, said air being compressed by the return of said pumping pistons, said air being supplied under pressure for scavenging the power cylinder of the products of combustion and means for supplying a fresh combustible mixture into the said cylinder.

2. In an improved percussive tool, a pair of connected cylinders having thereon a hammer, said cylinders comprising a power cylinder and a pumping cylinder, a piston in the pumping cylinder, a rod connected at one end to the piston, an anvil on the other end of the rod adjacent the hammer, a piston in the power cylinder, a second piston in the pumping cylinder connected to the piston in the power cylinder by a rod, an air inlet into the pumping cylinder, an air passageway leading from the pumping cylinder to the power cylinder, and means to supply fuel to the air passageway adjacent the power cylinder.

3. Improved percussive tool comprising a supporting rod and a power cylinder, a pumping cylinder connected to and so as to move with the power cylinder, a stop plate at the junction of the two cylinders, a piston in the power cylinder, a piston in the pumping cylinder fixed on the upper end of the supporting rod, a rod connected to the piston in the power cylinder and passing through the stop plate into the upper end of the pumping cylinder, and a piston fixed to the lower end of said rod and normally resting loosely upon the piston on the upper end of the supporting rod, said cylinder having inlets and discharge passageways.

4. Percussive tool according to claim 3, comprising exhaust ports in the wall of the power cylinder located so as to clear the top of the power piston in the raised position of the power cylinder, an outlet opening in the wall of the pumping cylinder located so as to come opposite to the space formed between the piston on the upper end of the supporting rod and the piston on the lower end of the rod connected to the power piston in the raised position of the cylinders, a pipe connected to said outlet opening leading to the head of the power cylinder through an inlet valve, and preferably through a carburetting device, and a one-way air inlet valve in the wall of the pumping cylinder located at, or approximately at, the same level as the said outlet opening.

DUNCAN MARLOR WILCOX. 

